Ameraucana/EE egg color question--is it always the same color?

This might be a dumb question, but say an EE lays a green egg one day--will they ever lay maybe a turquoise one the next day?

My understanding was that the blue color comes from the chicken's metabolism during the shell-making process, and the green is really a light brown coating that would otherwise make a pale brown egg. Does it happen that if a chicken had a diet change, it might make a more intense blue egg?

The reason I ask, I have one EE that has laid two perfect pastel sage-green eggs in a particular spot by the door. Today when I went in to check, there was an egg in a slightly different spot (by the door, just in a different pile of bedding) which was just a shade more blue. I can't get the color to come out in a photo, but trust me, it's a slightly different shade when I compare them on white paper. I have a total of five EEs, all the same age, so it could be any of them. I know the green eggs come from Morgaine, I checked her vent and she cackles sort of uniquely. Do I really have an egg from a different chicken, or might they be the same chicken?

They will always lay blue if they started blue and green if they started green, however, the intensity of the color will vary by the outside temps, i.e. if they are under heat stress, and where they are in their laying cycle as well. Usually, the eggs will get paler the longer they've been laying and when they take a break during a molt, the color comes back afterward.